Biodiesel fuel processing

ABSTRACT

Biodiesel is formed by blending an with a hydrocarbon fuel, preferably #2 diesel, gasoline, or kerosene. Water in the mixture, and other impurities, are removed by adding a coalescing aid such as naphtha, xylene or naphthalene and passing the mixture through a series of filters including a coalescing filter. Optional components that can be added to the fuel include cetane additives, lubricants such as trimethylbenzene and ethylene, as well as performance enhancers such as acetone.

RELATED APPLICATION

This application claims the benefit of provisional application No. 60/763,176 filed Jan. 30, 2006, entitled “Biodiesel Home Fueling Station”, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Biodiesel is a fuel formed from naturally obtained fatty acids, i.e., from either vegetable oils or animal fats. Traditionally, biodiesel has been formed by the transesterification of fatty acids. In this process, an alcohol, typically a lower alkyl monoalcohol, is reacted under basic or acid conditions with the fatty acids. This produces the monoalkyl ester of the fatty acids, as well as glycerin, water and other impurities.

These impurities, as well as other impurities that are naturally present in the fatty acid, must be removed. In particular, removing the water is somewhat problematic. The traditional method of doing so is a physical separation in which the transesterification reaction product is simply allowed to settle. The water will naturally separate from the esters, permitting physical separation.

This is time consuming, taking upwards of twenty-four hours. Relatively large quantities of material must be stored to permit separation. This is very costly because of the time requirement, and because of the capital equipment required to hold the material for a sufficient period of time to permit separation.

Non-esterified fatty acids can also be used in a biodiesel formulation, but these also have the same problems with impurities. There is significantly less water present, but this still has to be removed. Removal of a minor amount of water can be more difficult than removal of large amounts such as is present in the transesterification product.

Biodiesel must meet certain end use requirements as specified by ASTM D-6751. This sets maximum concentrations for various impurities such as carbon residue, sulfur red ash, sulfur, copper, free glycerin, total glycerin, phosphorus, sodium and potassium. Cetane ratings must also be met.

SUMMARY OF THE INVENTION

The present invention is premised on the realization that biodiesel can be formed from natural fatty acids without a transesterification reaction. According to the present invention, natural fatty acids are blended with kerosene or #2 diesel and a low viscosity, low molecular weight hydrocarbon which acts as a coalescing aid. The water and impurities dissolved in the water are then removed using a coalescent filter. Other impurities, such as glycerin, particulates, as well as polyaromatic compounds, can then be filtered out by a carbon or activated carbon filter. This reduces the overall time required to produce the biodiesel and, further, requires no transesterification reaction.

Preferred coalescing aids include naphtha and naphthalene. In addition to the coalescing aid, a cetane improving composition, acetone, and a lubricity aid such as trimethylbenzene, are added to the biodiesel formulation to further improve the performance of the product.

The objects and advantages of the present invention will be further appreciated in light of the following detailed description and drawings in which:

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a diagrammatic depiction of the filtration apparatus used in the present invention.

DETAILED DESCRIPTION

Biodiesel is produced by blending a combination of naturally occurring triglycerides, a lower viscosity hydrocarbon fuel, and a coalescing aid. The naturally occurring fatty acids can be obtained from any source, vegetable or animal. Preferably these triglycerides are liquid at room temperature and can be, for example, used fryer oil, corn oil, soy bean oil, palm oil, safflower oil, animal fats, and the like. Used motor oil can also be added but requires additional filtration. Collectively, these will be referred to as oils. Typically, these oils will include various amounts of impurities such as water, sulfur, potassium, other water soluble salts, and the like.

The oil should include a minimum amount of water to facilitate impurity removal. Generally, it is preferred to have about 0.4 ounces of water per gallon of the oil. Accordingly, if the source of the oil does not include sufficient water, water can be added. These oils can have a viscosity of 40 centistokes or more at 40° C. For use as a diesel fuel, the viscosity must be from 6-1.9 centistokes.

Accordingly, a hydrocarbon fuel is added to the naturally occurring oil to reduce its viscosity. Generally, about 12-30%, preferably about 15-20%, by weight of the hydrocarbon fuel will be added to the overall biodiesel composition. This is simply mixed together without any special equipment. The hydrocarbon fuel can be diesel fuel such as #2 diesel fuel, or any grade of kerosene or gasoline. A blend of these can also be used. If only diesel is added, about 30% #2 diesel may be required. Gasoline decreases the amount of hydrocarbon fuel needed, but significantly reduces the flash point. Therefore, a mixture of the two is preferred. Generally, about 2/1 diesel to gasoline (by volume) is preferred.

Next, a coalescing aid is added to the formulation. The coalescing aid can be any composition that will assist in the coalescence of the water in the fuel mixture. Generally, this will be a hydrocarbon composition that has a viscosity of less than 2 centistokes at 40° C., and a specific gravity of less than 1. Compositions that will assist in coalescing water in oil include naphtha, naphthalene, xylene and toluene. Preferred coalescing aids include solvent naphtha and toluene. Gasoline has some coalescing activity but is not considered a true coalescing aid due to its performance. Alcohols are also less preferred, as these are undesirable in diesel formulations.

The coalescing aid may be 100% naphtha or a blend of coalescing aids. The coalescing aid may include naphtha at about 50-100% by weight. This, in addition to acting as a coalescing aid, lowers the flash point of the biodiesel fuel. Xylene, of about 0-10% by weight can also be added. This further lowers the flash point, even lower than naphtha. Finally, naphthalene at about 0-40% by weight is desirable. This improves the combustion and reduces combustion pressure.

Generally about 0.25 ounces of coalescing aid per gallon is added to the fuel mixture. More or less can be used, depending upon the effectiveness of the particular coalescing aid as well as the water content.

If the diesel formulation does not have a high enough cetane rating to function as a diesel fuel, one can add a cetane additive. It is preferred to have a cetane rating of 50 or better. The amount of cetane additive will also vary depending on the source of the oil. Soybean oil has a naturally high cetane rating. A cetane additive, generally at about 0.15 oz/gal of fuel mixture, can be added to achieve the desired cetane rating. One preferred cetane additive is 2-ethylhexylnitrate, also referred to as cetane.

Because this formulation is naturally low in sulfur and the processing will reduce sulfur, a lubricant may be added. For example, 5% by weight of ethylene can be added as a lubricant. Other lubricants can include trimethylbenzene, either 1-2-4-trimethylbenzene, or 1-3-5-trimethylbenzene in a total of about 5 wt. %. Finally, 5% by weight of a lower molecular weight ketone such as acetone can be added to improve fuel efficiency. The cetane additive, lubricity additives, as well as the fuel efficiency improver (acetone) are optional components and may be omitted or increased as desired.

The preferred additive formulation includes:

Solvent Naphtha 45 w/w %  Naphthalene 10 w/w %  Cetane 30 w/w %  Ethylene 5 w/w % Trimethylbenzene 5 w/w % Acetone 5 w/w %

About 0.5 to about 1 ounce (preferably about 0.5 ounces) of the above additives are combined with each gallon of fuel mixture. This is allowed to mix in a tank or can be actively blended with an in tank mixer. Water can be added to establish the water content at 0.4 oz/gal.

The FIGURE shows a diagrammatic depiction of the apparatus 10 used to process the biodiesel formulation of the present invention. The apparatus 10 includes a mixing tank 12 where the oil and hydrocarbon fuel are mixed. Additional water can be added to the mixture in tank 12 to establish the desired water concentration, if needed. The coalescing aid along with the cetane additive, lubricant and fuel efficiency enhancer, if desired, are also added to the mixture in tank 12. The tank can include a mixer, if desired, but this is not generally required.

After about 30 minutes, the fuel mixture passes through line 14 to a coalescent filter 16 that is on the low pressure side of pump 18. The coalescent filter 16 is designed to remove substantially all of the waters leaving less than 0.35% by volume water in the fuel mixture. Generally, the filter can remove down to 0.0005% by volume, which is required if used motor oil is added to the diesel blend.

Pump 18 then directs the fuel mixture to a first ionic filter 20 designed to remove larger particles down to about 5 microns in size. The fuel mixture passes through line 22 to a charcoal filter 24 designed to remove impurities down to 3 microns, as well as to remove certain aromatic compounds. The fuel mixture then passes through a valve 26 that directs the fuel mixture either through a recirculation loop 28 or to a polishing filter 30, designed to remove particles down to 2 microns in size. If used motor oil is present, the filter should remove particles as small as 0.5 microns. The fuel mixture or biodiesel then is directed through line 32 to a tanker car for delivery.

This will be further appreciated in light of the following detailed description and examples.

EXAMPLE

A biodiesel formulation was formed by combining 100 gallons of degummed soybean oil, 12 gallons of #2 kerosene, 5 gallons of gasoline and 60 ounces of the preferred additive formulation. These were combined together, allowed to sit for 30 minutes, and run through the filtration apparatus described with respect to the FIGURE. In this embodiment, the polishing filter was a 2 micron polishing filter. The formulation was tested after processing and the results are shown in the Table below:

TABLE Test Description ASTM 6571 Method Result Flash point - deg F. D93 >200 Water and sediment D2709 <0.05 Kinematic Viscosity D445 4.3 Sulfated Ash - % mass D874 <0.02 Sulfur - ppm D5453 <0.0010 Copper Strip D130 #1 Centane D613 55 Cloud Point - deg C. D2500 −10 Carbon residue - % mass D4530 <0.02 Acid Number mg/gm D664 0.3 Free Glycerin - % mass D6584 <0.001 Total Glycerin - % mass D6584 0.23 Phosphorous - % mass D4951 <0.001 Distillation - temp 90% rec. deg C. D1160 330

All of these results are within acceptable limits for diesel fuel.

This process takes no more than about 30 minutes, the time required to allow the components to mix together in the tank 12 allowing the water particles to coalesce together, making them easier to remove with a coalescent filter. This process allows natural oils and fats to be incorporated into biodiesel without a transesterification reaction and with minimal processing and requiring minimal capital. The net effect is to reduce the cost of biodiesel while maintaining the quality.

This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims. 

1. A method of forming biodiesel comprising blending oil with a hydrocarbon fuel to form a fuel mixture having a water content; adding to said fuel mixture a hydrocarbon coalescing aid; and filtering water from said fuel mixture.
 2. The method claimed in claim 1 comprising filtering said water with a coalescent filter.
 3. The method claimed in claim 2 wherein said oil is selected from the group consisting of vegetable oil, animal fat, used motor oil, and mixtures thereof.
 4. The method claimed in claim 3 wherein said hydrocarbon fuel is selected from the group consisting of diesel fuel, kerosene, gasoline, and mixtures thereof.
 5. The method claimed in claim 2 wherein said coalescing aid comprises a hydrocarbon having a specific gravity having less than 1 and a viscosity less than 2 centistokes at 40 degrees C.
 6. The method claimed in claim 2 wherein said coalescing aid is selected from the group consisting of naphtha, xylene, naphthalene, toluene, and mixtures thereof.
 7. The method claimed in claim 2 further comprising adding a cetane agent to said mixture.
 8. The method claimed in claim 7 further comprising adding to said mixture a lubricant.
 9. The method claimed in claim 8 wherein said lubricant is selected from a group consisting of trimethylbenzene and ethylene, and mixtures thereof.
 10. The method claimed in claim 7 further comprising adding acetone to said mixture.
 11. The method claimed in claim 2 further comprising passing said fuel mixture through a particulate filter.
 12. The method claimed in claim 11 further comprising passing said fuel mixture through a carbon filter.
 13. The method claimed in claim 4 wherein said hydrocarbon fuel comprises at least about 12% of said fuel mixture.
 14. A method of forming a biodiesel composition comprising blending a triglyceride composition with a hydrocarbon fuel selected from the group consisting of diesel fuel, gasoline, kerosene, and mixtures thereof, to form a fuel mixture; establishing a water content in said fuel mixture of at least 0.4 ounces of water per gallon of fuel mixture; adding to said fuel mixture a coalescing aid selected from the group consisting of naphtha, xylene, naphthalene, toluene, and mixtures thereof in an amount equal to at least about 0.25 oz/gal of said fuel mixture; and removing water from said fuel mixture with a coalescing filter.
 15. A biodiesel fuel composition comprising at least about 75% by weight of a triglyceride, at least 12% by weight of a hydrocarbon fuel, and about at least 0.25 oz/gal coalescing aid selected from the group consisting of naphthalene, xylene, naphtha, toluene and mixtures thereof, a cetane additive, and a lubricant selected from the group consisting of trimethylbenzene, ethylene and mixtures thereof. 